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1 Dorsal fins are found on the back of the fish. 2  There may be up to three of them. 3  The fish uses this fin for balance in the water and sudden movements. 4  Caudal fins are also known as tail fins.5  This is what we refer to as the fish's tail. 6  Anal fins are on the ventral (bottom) surface of the fish, behind the anus. Dorsal fins are found on the back of the fish. 2  There may be up to three of them. 3  The fish uses this fin for balance in the water and sudden movements. 4  Caudal fins are also known as tail fins.
The cephalaspids had one or two dorsal fins and an anal fin as well as a pair of primitive pectoral fins. By the time of the placoderms pelvic had also evolved. The shape and structure of a fish's fins reflect both its lifestyle and its evolution.n some species they are used to hold on to the substrate while in others they allow the fish to walk, or even to fly. Without fins a fish would just be a fancy worm. The earliest known fishes had fins, albeit not as many as modern fish, but even the most ancient and primitive agnatha had a caudal fin.